Automatic system for detecting printing faults on metallized strips or any other printing support comprising a predominance of specular color surfaces

Abstract

This automatic system ( ) detects printing faults on metallized strips ( ) or any other printing support comprising a predominance of specular color surfaces. The said system, arranged in a blackout casing ( ), comprises an arm ( ) on which there can move automatically a lighting unit ( ) provided with a video camera ( ). The camera has a variable-focus lens ( ) which, through a semi-transparent filter ( ) disposed in an oblique position in front of the lens, continuously films a portion of the strip ( ) of a format ( ) of variable size. The illumination of this strip portion is provided by two direct-illumination flashlights ( ), provided primarily to illuminate the non-specular surfaces of the strip, and by two other indirect-illumination flashlights ( ), advantageously provided to illuminate the specular color surfaces. One of the two flashlights ( ) comprises a translucent flat diffuser ( ) disposed on its leading front surface and oriented preferentially in the direction of the semi-transparent filter ( ), while the other flashlight ( ) is oriented in the direction of the surface of a concave and opaque diffuser ( ). Enclosing the semi-transparent filter ( ), the diffuser ( ) is mounted at its center on a sleeve ( ) which provides the mechanical and optical connection between the diffuser ( ) and the lens ( ) of the camera ( ).